Vasovagal reactions in blood donors
Tomasulo P, Kamel H, Bravo M, et al.
Interventions to reduce the vasovagal reaction rate in young whole blood donors
Transfusion 2011; ahead of print (doi: 10.1111/j.1537-2995.2011.03074.x).
Vasovagal reactions are the most common potentially severe adverse events of blood donation. Although most cases are mild and of no immediate consequence to the donor, they are known to decrease the return rate, particularly when they occur in the first one or two donations. Moreover, susceptible individuals may faint at the sheer sight of other people experiencing an adverse event (“epidemic fainting”), putting the staff of the blood centre in a situation difficult to manage. Previous studies had shown that young girls, weighing near to the minimum donor weight (50 kg), at their first donation, were particularly susceptible. Among the characteristics associated with reactions, the donor’s blood volume is a stronger predictor than his or her body weight.
The Authors of the present study introduced three interventions aimed at reducing the reaction rate and, in this article, reported the frequency of adverse events in the year before and the year after their implementation. The interventions were: (i) deferral of donation if the estimated blood volume (calculated from height, weight and sex) was less than 3.5 L, as the volume of blood to be collected (525 mL) would have represented more than 15% of the circulating volume; (ii) instructing donors to engage in so-called “applied muscle tension”, i.e. a vigorous isometric contraction of buttocks and legs, sustained for 5 seconds and followed by 5 seconds of rest, throughout the phlebotomy period; (iii) encouraging donors to drink approximately 500 mL of water in the 30 minutes preceding the phlebotomy. The interventions were directed to donors less than 23 years old, because they were considered the most reaction-prone group. Reactions were classified as mild, moderate or severe, according to commonly accepted, albeit somewhat arbitrary, criteria. However, the Authors also reported separately on the occurrence of loss of consciousness, as the recording of this outcome is not liable to subjective interpretation.
During the study period, 213,031 donations were made by donors under the age of 23 years (60% from females). In the year before implementation of the intervention, 16.3% of the donations from young female donors exceeded 15% of the estimated blood volume. In the year after, such donations accounted for less than 0.7% of the total: a decrease of 96%, demonstrating thorough application of the first intervention. Male donors very rarely exceeded the 15% limit, either before or after the intervention (0.01% or less). The overall reaction rate decreased from 32.7 to 24.8 per 1,000 donations (−24%, p≤0.0001). Similarly, the frequency of loss of consciousness dropped by 22% (from 7.4 to 5.8 per 1000 donations, p≤0.0001). All hypotensive reactions decreased, regardless of the degree of severity. The impact of the second and third interventions was evaluated in the donors with an estimated blood volume ≥3.5 L. The overall reaction rate decreased from 29.6 to 24.7 per 1,000 donations (−17%) and the difference was statistically significant for both males and females. The improvement was not explained by differences in the frequency of first-time donors or in ethnic origin between the years before and after the implementation of the interventions. A multivariate analysis confirmed that the three interventions had been effective (odds ratio, 0.92; 95% confidence interval, 0.87–0.97), but the known risk factors, such as younger age (17–18 years versus 19–22 years), female sex, first-time donor status, ethnicity, pulse rate, and, most markedly, blood volume, still retained their importance.
The Authors probably expected a greater improvement in the reaction rate. In fact, according to prior estimates, the first intervention alone should have decreased the reaction rate in the study population by at least 30%. Each of the other two interventions had previously been found to be effective in prospective studies. The Authors commented that, reviewing internal audit data, it appeared that the last two interventions had not been implemented perfectly: providing the explanations on how to perform applied muscle tension was found embarrassing by the staff; moreover, some centres supplied 250 mL bottles of water instead of the intended 500 mL ones. I would add that the literature is not homogeneous on what is denoted by “applied muscle tension”: some describe it as 5-second cycles of isometric tension of the muscles of the whole body or of the major muscle groups of the arms and legs, some only include thighs, buttocks and stomach, while in this study only buttocks and legs were involved. It is not clear whether these differences are of any importance.
Gamma irradiation of red blood cells
Zimmermann R, Schoetz AM, Frisch A, et al.
Influence of late irradiation on the in vitro RBC storage variables of leucoreduced RBCs in SAGM additive solution
Vox Sang 2011; 100: 279–84.
European and American guidelines on the irradiation of red cell concentrates differ in that the former require that irradiation should not be performed after the 14th day of storage and the total duration of storage should not exceed 28 days, while the latter only require that red cells should not be stored more than 28 days after irradiation. To my knowledge, there is no evidence supporting the European decisions, which imply that the damage caused by irradiation increases with the duration of storage before irradiation. Experimental data on this subject are, however, scanty. The present study yields some more information, albeit limited to a few in vitro parameters.
A total of 160 pre-storage leucoreduced red cell units in SAGM were divided into four groups: 40 units were irradiated with 30 Gy of gamma rays on day 14 of storage, 40 on day 28, 40 on day 35, and the remaining were not irradiated (controls). The following in vitro parameters were evaluated before and after irradiation and every week up to day 42: potassium, phosphate, glucose, free haemoglobin, and lactate dehydrogenase in the supernatant; blood counts, haemoglobin, haematocrit, pH, ATP and 2,3-diphosphoglycerate (2,3DPG) in the red cell suspension.
In comparison to the control units, the irradiated units contained more free haemoglobin, beginning from a week after irradiation. Throughout the storage period, the increase in the average free haemoglobin levels in the groups of irradiated units grossly corresponded to the duration of storage after irradiation. However, before day 42, no blood unit showed greater than 0.8% haemolysis. Extracellular potassium manifested a similar tendency, with the exception that the difference between irradiated and control units was already very large a week after irradiation. This behaviour has been noted in most other studies and clearly shows that potassium is not released because of haemolysis alone. A week after irradiation, extracellular potassium in all groups of irradiated units reached similar levels, which exceeded those reached by control units on day 42. ATP and 2,3DPG decreased during storage, without notable differences between the groups. The Authors concluded that red cells can be irradiated between the 14th and the 28th day of storage and subsequently stored for a week.
The Authors did not study either red cell deformability or vesiculation, nor did they report on mean corpuscular volume, although they mentioned it in the Methods section. Their conclusions are, therefore, based on two parameters only, known to represent aspects of the damage induced by gamma irradiation: haemolysis and potassium release. However, the present results are most appropriately interpreted in the light of previous experiments (Moroff G, Holme S, AuBuchon JP, et al. Transfusion 1999; 39: 128–34) in which the 24-hour recovery of irradiated red cells was studied. Moroff et al. irradiated red cell units on day 1, 14 or 26 of storage and transfused them 2, 14 or 28 days after irradiation. With respect to non-irradiated units, the 24-hour recovery of irradiated units was significantly decreased after 28 days, but not after 2 or 14 days. Moroff et al. concluded that in vivo recovery progressively decreased with the storage after irradiation. The duration of storage before irradiation did not influence the difference between irradiated and non-irradiated units appreciably. The results of the present study are in perfect agreement. The available data, therefore, fully support the American but not the European guidelines. It is quite clear that it is preferable to irradiate the red cell units just before transfusion. In that way, the effects on both in vivo recovery and extracellular potassium levels would be minimised.
Overnight hold at ambient temperature before component preparation
Transfusion, the journal of the American Association of Blood Banks, recently devoted a supplement (Volume 51, Supplement 1) to the issue of prolonged storage (“overnight hold”) at ambient temperature before the separation of whole blood into components.
Platelets are damaged by even a short stay at low temperature. On the other hand, red cells and plasma retain their properties better at low temperature. As a consequence, platelets are usually separated within a few hours of the collection of whole blood or, if this is impossible, they are not produced at all. Delaying the production of platelets would be a great advantage from an operational standpoint. The articles reviewed below examine the effects of prolonged storage at ambient temperature on blood components. With a single exception, all of them come from the cited supplement.
Moroff G, AuBuchon JP, Pickard C, et al.
Evaluation of the properties of components prepared and stored after holding of whole blood units for 8 and 24 hours at ambient temperature
Transfusion 2011; 51: 7S–14S.
This is the only article of the series providing data on in vivo recovery and survival. Healthy donors donated blood (450±45 mL) on two occasions, at least 70 days apart. On one occasion, the whole blood unit was stored before centrifugation for 7–8 hours in an insulated box containing butane-1,4-diol cooling plates, to maintain the temperature between 20 and 24 °C. On the other occasion, the whole blood unit was stored in the same conditions as described above for the first 8 hours and then moved to a platelet incubator and maintained at 20–24 °C, without agitation, for the next 16 hours. The blood components were not leucoreduced. The red cells were suspended in 100 mL of AS-1 (Adsol). The platelets were prepared by the platelet-rich plasma method.
The in vivo 24-hour red cell recovery was measured after 35 and 42 days of storage, by both the single- and the double-label method. After 35 days, the recoveries (%, N=8–9) of the 8-hour and the 24-hour hold units were 79.2±4.3 and 79.4±3.9, respectively, with the single label method, and 79.7±6.5 and 83.4±7.2 with the double label method. The differences were not statistically significant. After 42 days, the recoveries (N=17) were 76.0±5.4 and 72.9±6.5 with the single label method (p=0.036), and 75.5±5.8 and 73.5±8.0 (not significant) with the double label method. These results leave the question open as to whether there is any real difference in recovery after 42 days of storage. In any case, any difference should be small, around 2–3%. The survival (T50, days, N=8) was studied after 42 days of storage only and showed no difference between units held for 8 hours or 24 hours. As expected, the 2,3DPG levels (μmol/g Hb) after the hold period were substantially different (8hour hold: 9.8±1.4; 24-hour hold: 4.6±1.5; N=18; p<0.05). However, other in vitro parameters (ATP, haemolysis, pH, extracellular sodium and potassium), determined after 42 days, showed no significant differences.
The in vivo platelet recovery (%) and platelet survival (T50, hours, N=18) of units held for 8 hours and 24 hours, measured after 5 days of storage, were not significantly different (recovery: 51.1±14.9 versus 50.6±17.7; survival: 167.9±30.7 versus 152.9±51.5; N=18). Likewise, no significant differences were found in in vitro platelet parameters (volume, platelet content, pH, morphology score, response to hypotonic stress, ATP).
As regards plasma, factors V and VIII were determined after the hold period (N=18). The concentration of factor V was slightly lower in the units held for 24 hours, but the difference was not statistically significant. On the other hand, the concentration of factor VIII was 12–33% lower in the units held for 24 hours and this was a statistically significant difference (≥p 0.0006).
The Authors concluded that the few differences in the quality of the blood components prepared with an 8-hour and a 24-hour hold were not clinically important.
van der Meer PF, Cancelas JA, Cardigan R, et al.
Evaluation of overnight hold of whole blood at room temperature before component processing: effect of red blood cell (RBC) additive solutions on in vitro RBC measures
Transfusion 2011; 51: 15S-24S.
This international multicentre study from the Biomedical Excellence for Safer Transfusion (BEST) Collaborative compared blood components prepared after a short (<8 hours) or a long (24–26 hours) hold at a temperature of 18–25 °C and also studied the effects of different red cell additive solutions. Pools of four fresh donations of whole blood were divided into four groups: group A units were processed within 8 hours of the collection of the last unit of the pool; the red cells were suspended in SAGM; group B-D units were processed after 24–26 hours: group B red cells were suspended in SAGM, group C red cells in PAGGSM (phosphate-adenine-guanosine-glucose-saline-mannitol) and group D red cells in ErythroSol-4. Eight of the nine participating centres prepared platelet concentrates from the whole blood units: six by the buffy coat method, two by the platelet-rich plasma method. All red cell units were leucoreduced by filtration.
A total of 37 pools were studied. Group A units were processed after 3±1 hours; group B-D units after more than 24 hours. Comparing the groups after the hold at ambient temperature but before processing into blood components, the 24-hour hold caused a marked decrease in 2,3DPG (−65%, p<0.001), a small increase in platelet count (from 192±31 to 204±26x109/L; p<0.01) and greater platelet activation, as measured by CD62P expression (from 14±8 to 22±11%, p<0.01). In the buffy coat, however, CD62P expression actually decreased (from 25±12 to 16±10%; p<0.01) and the platelet count substantially increased (from 1,556±561 to 1970±345x109/L, +27%, p<0.001), after the 24-hour hold. As regards the red cell additive solutions, group D units (suspended in ErythroSol-4) showed greater ATP levels throughout the 7 weeks of storage, but from the 5th week the differences were small and clinically unimportant. 2,3DPG levels were very low in all groups from the 3rd week onwards. Haemolysis was significantly greater in group B units but did not exceed the 0.8% limit at the usual maximum storage time (42 days) in any group. There were no differences in extracellular potassium between the groups. The platelet preparation method obviously influenced the amount of red cells originally present in the whole blood, recovered in the red cell unit (buffy coat: 79±4%; platelet-rich plasma: 85±6%), and the amount of plasma (buffy coat: 84±7%; platelet-rich plasma: 53±7%). The Authors remarked, however, that with the buffy coat method a unit of plasma is sacrificed to be used as a suspension medium for the platelet concentrate.
In conclusion, as regards the red cells, prolonged hold at ambient temperature negatively affected 2,3DPG levels, but only in the initial phase of the storage period. On the other hand, this study confirmed earlier observations that an overnight hold has beneficial effects on in vitro platelet yield.
Veale MF, Healey G, Sparrow RL
Effect of additive solutions on red blood cell (RBC) membrane properties of stored RBCs prepared from whole blood held for 24 hours at room temperature.
Transfusion 2011; 51: 25S–33S.
This is a satellite study to the previous one in this Press Review. The Authors aimed at a better discrimination between the three additive solutions (SAGM, PAGGSM, ErythroSol-4), which in the previous study had shown only minor differences. The experimental design was similar to that of the previous study, with the exception that only groups B-D were examined (see above). The whole blood units were leucoreduced after the overnight hold. They were processed into red cells and plasma only. Besides common storage parameters, the Authors measured osmotic fragility, red cell size and shape, the release of microparticles (vesiculation), and adhesion to endothelial cells.
Four pools of three whole blood donations were studied. Both PAGGSM and ErythroSol-4 exerted a protective effect on haemolysis, an effect which was more marked after 4 weeks of storage. By contrast, extracellular potassium was substantially identical in all additive solutions. The red cell shape was indirectly studied by flow cytometry, comparing forward and side scatter. The Authors inferred from their observations that red cells stored in PAGGSM and ErythroSol-4 had more irregular surface texture and shape than red cells stored in SAGM. The mean corpuscular volume (MCV) increased during storage in SAGM, but remained constant in PAGGSM and decreased in ErythroSol-4. These findings are in agreement with what was previously known. In particular, ErythroSol-4 is hypotonic and red cells swell immediately when they are suspended in this solution, regaining in part their previous volume during storage. This article does, however, report that, throughout the storage period, red cells stored in ErythroSol-4 have a lower MCV than cells stored in the other additive solutions, which is very surprising. Another surprising finding concerned osmotic fragility. During storage, the red cells in PAGGSM and ErythroSol-4 showed greater resistance to osmotic lysis than did red cells in SAGM. What is frankly unbelievable, however, is that at day 42 of storage, the red cells in all additive solutions were less fragile than at day 1. The Authors did not offer any explanation or comment. Vesiculation was estimated by flow cytometry, counting microparticles (diameter <1 μm) containing glycophorin A or phosphatidylserine. As already observed in other studies, the release of glycophorin A-positive microparticles followed an exponential curve in all additive solutions, with an evident increase over the baseline starting from the 4th week. Red cells in both PAGGSM and ErythroSol-4 released fewer microparticles than those in SAGM, with ErythroSol-4 slightly better than PAGGSM. Phosphatidylserine-positive microparticles followed a similar behaviour. Red cells in ErythroSol-4 showed increased adherence to endothelial cells, particularly after 42 and 49 days of storage. The Authors admitted that both the biological mechanism and the clinical significance of this phenomenon are unknown.
Summarising their results, the Authors remarked that PAGGSM and ErythroSol-4 were superior to SAGM as regards haemolysis, osmotic fragility and vesiculation, all aspects evidencing improved maintenance of membrane properties; on the other hand, red cells in ErythroSol-4 appeared dehydrated and more adherent to endothelial cells; therefore, PAGGSM emerged as the preferable additive solution.
In my opinion, however, the findings of this study are far from being clearly demonstrative and raise more doubts than answers: the results on osmotic fragility are difficult to accept; both vesiculation and increased adherence to endothelial cells are phenomena occurring mainly in the late phases of the storage period; there is no proof that they correlate with clinical efficacy and safety.
Dijkstra-Tiekstra MJ, van der Meer PF, Cardigan R et al.
Platelet concentrates from fresh or overnight-stored blood, an international study
Transfusion 2011; 51: 38S–44S.
This study concerned platelet concentrates prepared by the buffy coat method. Three different protocols were compared: buffy coats separated and processed within 2–8 hours from the collection (fresh/fresh); buffy coats separated within 2–8 hours but processed after 20–24 hours (fresh/stored); buffy coats separated and processed after 20–24 hours (stored/fresh). The platelet concentrates were derived from pools of four to six buffy coats plus plasma. All were leucoreduced.
Each of the six participating centres tested six platelet concentrates per protocol. On day 1, the platelet content (x109) per pooled concentrate was 201±75 with the fresh/fresh protocol, 285±55 with the fresh/stored protocol, and 338±55 with the fresh/stored protocol (p<0.05 for all comparisons). Comparing the results against the European guidelines (60x109 platelets for each concentrate in the pool), 25/35 fresh/fresh, 6/36 fresh/stored, and 3/36 stored/fresh concentrates did not meet the specifications. Using the American and Canadian threshold (55x109), the numbers were 22/35, 3/36, and 2/36, respectively. The Authors pointed out the greater variability of the counts in fresh/fresh concentrates. The values of glucose, pH, and pO2 were higher in fresh/fresh concentrates, while the opposite was true for pCO2 and lactate. However, all metabolic parameters remained within normal limits, regardless of the protocol. Platelet activation, measured as CD62P expression, was significantly greater in fresh/fresh concentrates, throughout the storage period (7 days). At the end of storage, the hypotonic shock response was greater in stored/fresh concentrates, while there were no significant differences in the aggregation induced by ADP or collagen.
The Authors commented that, most probably, the only clinically important finding of their study was the impressive difference in the platelet content of the concentrates (+68%, stored/fresh versus fresh/fresh). The Authors attributed the difference to the activation of platelets during the collection of whole blood, which presumably provoked the formation of aggregates when the platelets were concentrated in the buffy coat. By contrast, the fresh/stored and, even more, the stored/fresh protocol allowed ample time for the platelets to de-activate or disaggregate.
van der Meer PF, Cancelas JA, Vassallo RR, et al.
Evaluation of the overnight hold of whole blood at room temperature, before component processing: platelets (PLTs) from PLT-rich plasma
Transfusion 2011; 51: 45S–49S.
This article contains the data on platelet concentrates prepared by the platelet-rich plasma method, collected within the BEST study reviewed above (van der Meer PF, Cancelas JA, Cardigan R, et al. Transfusion 2011;51:15S–24S). Experimental conditions were the same as described above. Immediately after preparation, the platelet concentrates prepared after the overnight hold contained significantly more platelets (90±6x109 versus 69±21x109, +30%, p<0.05). They also had lower pH, glucose, and bicarbonate, higher lactate and pCO2, and a better hypotonic shock response. Platelet activation (assessed by CD62P expression) was similar after both the 8-hour and the 24-hour hold. All these differences decreased or disappeared completely by the end of the storage period, including the platelet content, which increased in the concentrates prepared after the 8-hour hold. The Authors commented that when platelets are processed rapidly after donation, they tend to form small aggregates which slowly dissolve during storage.
Cardigan R, van der Meer PF, Pergande C, et al.
Coagulation factor content of plasma produced from whole blood stored for 24 hours at ambient temperature: results from an international multicenter BEST Collaborative study
Transfusion 2011; 51: 50S–57S.
This study, too, comes from the BEST Collaborative and had the same experimental conditions as those of the others reviewed above. The present study was aimed at evaluating the effect of a prolonged hold at ambient temperature on the concentration of single coagulation factors and on global tests of haemostasis. As expected, the levels of factor VIII were significantly lower in the units held for 24 hours (−23%, p<0.01). Most other coagulation factors were unaffected, but factors II, IX, and X showed minor (<5%) but statistically significant decreases. As regards natural anticoagulants, antithrombin was unaltered but protein C and S activities diminished slightly (−6% and −14%, respectively). Assays of thrombin generation or clot formation (rotational thrombelastometry) showed only minor or no differences. The Authors concluded that, in all probability, the differences detected were not clinically important.
Lu FQ, Kang W, Peng Y, Wang WM
Characterization of blood components separated from donated whole blood after an overnight holding at room temperature with the buffy coat method
Transfusion 2011; ahead of print (doi: 10.1111/j.1537-2995.2011.03137.x).
Whole blood donations (400 mL) in CPDA were processed into components either after 6–8 hours or after an overnight hold. In both cases, the whole blood units were stored at room temperature without active cooling.
The platelet concentrates were produced by the buffy coat method and were stored for 5 days. The red cells and the platelet concentrates were leucoreduced before storage.
There were 30 units in each group. On day 1, the red cell units prepared after the overnight hold had significantly higher levels of ATP and lactate and lower levels of 2,3DPG and pH. These differences rapidly disappeared during storage. Haemolysis was slightly higher, throughout the storage period, in units held overnight, but, conversely, extracellular potassium was lower from day 14 onwards. Units held overnight had a significantly higher platelet yield: 971±130x109/L versus 879±139x109/L, +10%, p<0.05). Metabolic parameters (pO2, pCO2, glucose, lactate) of platelet concentrates showed minor initial differences, which were lost during storage. CD62P expression and annexin V binding behaved in a similar way. Conversely, the hypotonic shock response was slightly better in conventionally prepared units on days 4 and 5 only.
Plasma from units prepared conventionally or after overnight storage had similar coagulation factor concentrations, except for factor VIII, whose levels were significantly lower in the latter units (0.94±0.22 U/mL versus 1.17±0.32 U/mL, −20%, p<0.05). The Authors concluded that blood components prepared after an overnight hold are of acceptable quality.
The articles reviewed above add to previously published studies which showed that platelets benefit from an extended rest before preparation. A plausible explanation is that platelets get activated during collection and need time to de-activate. Otherwise, they form aggregates, presumably when they are concentrated by centrifugation, thus lowering the platelet yield. The magnitude of this effect seems to be greater when platelets are prepared soon after collection: in other words, the shorter the interval between collection and preparation, the greater the difference in yield. The buffy coat method seems to be more influenced than the platelet-rich plasma method. Probably, platelet aggregates are definitively lost within the red cell layer in the former method, while in the latter they are still present in the concentrate and can slowly disaggregate during storage.
As regards the red cells, all studies concordantly showed that an overnight hold slightly increases haemolysis and decreases 2,3DPG. The latter difference disappears after the first 2 weeks of storage. Probably neither effect is clinically significant. The few data on in vivo recovery are inconclusive but suggest that if there are real differences, they should be around 2–3% and not likely to be clinically significant. A similar conclusion can be reached regarding the loss of factor VIII activity in plasma.
None of the above studies concerned microbiological safety, but the pertinent literature suggests that this could actually be improved by a prolonged rest at room temperature, as leucocytes are allowed more time to ingest bacteria.
The practical advantages of delaying the preparation of platelets after collection are readily apparent. This approach has already been used in the Netherlands and a few other countries for many years now. The above studies confirm that it warrants much wider application in the near future.